Not only does this disincentivize HR from running fake vacancies or stringing multiple candidates on just to keep their options open, but it also solves the problem of unemployed people job-searching effectively working full-time for free. The fact that companies would have to pay to hire workers would mean they try to make the selection as short and effective as possible.
The hiring process has moved further and further from the company and is controlled by a bunch of middle-man companies who found a niche and made an industry out of it. No wonder hiring has become more expensive and riskier for a corp.